This invention relates to an operation circuit for a load. In particular this load can be a discharge lamp, especially a compact fluorescent lamp.
Discharge lamps and other loads are operated by means of operation circuits or powering circuits which comprise e.g. a half bridge oscillator with AC power supply. The AC power supply is rectified by a rectifier and smoothed by a relatively large electrolyte capacitor. This half bridge oscillator produces a high-frequency AC power and thus provides for a discharge lamp operation without flicker or acoustic noise.
One major disadvantage of discharge lamps compared to incandescent lamps is the lack of a dim function. However, there is one recent solution in prior art which has resulted in an improvement at this point. According to this proposal, an interruption of the power supply of an operation circuit for a discharge lamp is used so to say as a trigger signal for switching to a different operation state with a larger or a smaller lamp current when the lamp starts again. In this way, two different operation states with different lamp currents can be discriminated and switched and thus the lamp power can be reduced similar to a dim function. This prior art is given in EP 0 488 002 B1 and the corresponding priority application DE 40 37 948.